1. Technical Field
The present invention relates to a semiconductor device, and more particularly, to a method of fabricating a semiconductor device.
2. Related Art
Semiconductor memory devices, which store information such as data or program commands, are classified into dynamic random access memories (DRAMs) and static random access memories (SRAMs). DRAMs are memory devices which read or write information therein and store information therein. Although the DRAMs read/write information therefrom/therein, data stored in the DRAMs is lost when the information is not periodically rewritten within a given time period. DRAMS are required to be continuously refreshed, but have been widely used because it is possible to produce them at a low cost per memory cell and with a high degree of integration.
Typically, one memory device, that is, one memory cell, includes a transistor and a capacitor. The capacitor has a structure in which a dielectric layer is interposed between two electrodes. Capacitance of the capacitor is proportional to a dielectric constant of the dielectric layer and an electric surface area of an electrode and inversely proportional to a space between electrodes, that is, a thickness of the dielectric layer. Various methods have been suggested to fabricate a high capacitance capacitor. Such methods include using a dielectric material having a high dielectric constant, reducing a thickness of the dielectric layer, increasing a surface area of a lower electrode, or reducing a space between electrodes.
However, as the dimensions of a device are gradually reduced due to an increase in the degree of integration of the semiconductor memory device, it becomes difficult to ensure a sufficient surface area of the lower electrode. In addition, although it is possible to increase the dielectric constant to increase the capacitance of the capacitor, an increase in the dielectric constant is limited without also increasing the electrode's surface area. Thus, research on improvements in the structure of a lower electrode has continuously progressed and a three-dimensional (3D) concave type or a cylinder type capacitor has been developed to increase the electrode surface area.
Various levels of power are required to operate a capacitor in a cell area and other components in other areas including the peripheral circuit area. However, noise is accompanied by the power supplied to operate the capacitor. A reservoir capacitor is used to remove the noise. Reservoir capacitors are simultaneously formed in areas, including a peripheral circuit area, when transistors are formed in the cell area. At this time, many reservoir capacitors are formed in various areas in the semiconductor device. However, if the number of reservoir capacitors increases, and the degree of integration of the semiconductor device increases, an electric short between adjacent reservoir capacitors or between a reservoir capacitor and an underlying metal interconnection may occur. A semiconductor device or a method of manufacturing the same that prevents such problems is necessary.